Relays is relays. There are a couple of series of relays that are quite
universal. The 5 prong you describe is called a "change-over" relay in
that, as you say, 87a is the default path and 87 is the switched path.
Beware as there are some 5-term that are normally open and close both 87a
and 87b.. "double make relays" The pictures on the relays are pretty
self-explanatory. The numbering you have is typical European terminal
markings. In your case 85 and 86 are the coil terminals and it doesn't
matter how they're connected. 87's are alway the "consumer". 30 is always
the power for the "consumer". There are 4 terminal relays that do not have
87a, but these are being discontinued as not connecting 87a is the same as
not having it. As far as amperage goes 30 is probably fine and 40 is ok
too. The specs on the pump you bought will tell you the amp draw. Just make
sure the relay is rated above that. I hope I haven't confused you. But from
your original post, everything you're doing is correct.
HTH Peter C.
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At 11:33 PM 9/16/1999 , William M. Gilroy wrote:
>"William M. Gilroy" wrote:
>>
>> I have a rather stupid question about relays and I am sure someone
>> on the list can help. Here goes. I have a 30 amp relay that
>> has the following markings on the terminals: 30, 85, 86, 87, 87A.
>> My understanding of the terminals is this:
>>
>> 30 = power into the relay
>> 85 = power that cause the relay to switch
>> 86 = ground for 85 and relay
>> 87a = power when the relay is inactive
>> 87 = power when the relay is active (when there is power on 85)
>>
>> My question is have I correcttly labeled 85 and 86? Does it matter
>> if I reverse the power and ground on 85 and 86? Would that affect
>> how the relay function. I would like to get this right the first
>> time, that way my fuel pump will work.
>>
>
>A couple of other things. I have two relays from different makers,
>but the are functionally the same according to the diagram on them.
>The first is a Hella relay, part number 4RD 960 388-46 and the second
>is a Hamsar, part number 42-032. The Hella has a plastic mounting
>tab while the Hamsar has a metal mounting tab. I am not sure if the
>metal mounting tab is connected to the ground lead, number 86, since my
>ohm meter just went south. One other thing they are 40 Amp relays
>not 30 Amp.
>
>
>Bill Gilroy
>77 Midget
>90 Shar-Pei
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